CN101508470A - Process for producing stephanoporate one-dimensional nano-cobaltic-cobaltous oxide - Google Patents

Abstract

The invention discloses a preparation method of porous one-dimensional nanometer cobalt tetroxide, which includes the following steps: a) synthesis step: mixing divalent cobalt salt with urea solution at room temperature, and reacting for 0.5-12 hours at a temperature of 80-120°C ; b) Filtration and washing process: filter, wash and dry the synthesized solid product to obtain the nanostructure of dry cobalt hydroxide; c) Calcination process: place the product obtained in the filtering and washing process at 200-400 °C Heating at low temperature for 1-2 hours, then cooling to room temperature. Compared with the prior art, the present invention has uniform nano-powder particles, good dispersibility, and better cleanliness; only cobalt source is used as the precursor, and no crystal seed needs to be added; the yield is high, the cost is low, and the production process is short. The prepared tricobalt tetroxide has a very high specific surface area, which can greatly improve the performance of the battery when applied to the lithium ion battery.

Description

Preparation method of porous one-dimensional nano cobalt tetroxide

technical field

The invention relates to a preparation method of a nanometer metal oxide, in particular to a preparation method of a porous one-dimensional nanometer cobalt trioxide which can be used as a raw material of lithium cobaltate, a cathode material of a lithium ion battery.

Background technique

Lithium-ion batteries have the advantages of high voltage, stable discharge, high-current discharge performance, high specific energy, no pollution, and good cycle performance. In recent years, the lithium-ion battery industry has become increasingly mature, so it is widely used in various products such as mobile phones, computers, and automobiles. With the continuous improvement of the performance of lithium-ion batteries, the research on cathode materials for lithium-ion batteries has also been put forward higher requirements. Cobalt tetroxide is an important raw material for the preparation of lithium cobalt oxide, the positive electrode material of lithium-ion batteries. Its physical and chemical properties will have a greater impact on the positive electrode material lithium cobalt oxide and the battery. In addition to high purity and tap density, battery-grade cobalt tetroxide is required. There are still certain requirements for its shape and particle size distribution. Research and development of lithium-ion battery materials with high specific surface area, high specific capacity, high chemical stability, long cycle life and good safety is one of the main tasks to improve the application performance of lithium-ion batteries.

Common methods for synthesizing Co ₃ O ₄ are as follows:

1. Solid-phase method: it mainly mixes cobalt-containing compounds and lithium salts in a certain ratio, roasts them in air for a certain period of time at a given temperature, and cools to room temperature to obtain the product. However, the products prepared by the above methods have uneven particle size distribution, are easy to agglomerate, and have poor electrochemical performance. After 10 cycles, the specific capacity is from 1000mAh/g to below 100mAh/g. Therefore, its industrialization is difficult.

2. Precipitation method: mainly adopt cobalt salt and precipitant (sodium carbonate, ammonium oxalate, etc.) method, which discloses a technical scheme of using cobalt oxalate as the raw material for calcination and decomposing it into tricobalt tetroxide after three-step calcination. The temperature and equipment requirements for calcination are very high, which increases the production cost virtually, and the particle distribution of the product is uneven , it is difficult to meet the current requirements for battery performance improvement, which ultimately affects the industrialization of products.

Chinese patent CN1948167A discloses a method for preparing cobalt trioxide nanotubes. The method uses a soluble salt solution containing divalent cobalt ions as a raw material, adds ammonia water and stirs to form a precipitate, and then reacts the precipitate and inorganic salt in a closed container at high temperature for more than a dozen hours to obtain cobalt tetraoxide nanotubes. Although the method obtains nanometer one-dimensional cobalt tetroxide, the reaction time is long, the raw material types introduced are many, and the particle size distribution is uneven.

Contents of the invention

The technical problem to be solved by the present invention is to provide a preparation method of porous one-dimensional nanometer cobalt tetroxide with simple process and uniform particle size distribution.

The technical scheme for solving technical problems of the present invention is: the preparation method of porous one-dimensional nano-cobalt trioxide, comprising the following steps:

a) Synthesis process: mix divalent cobalt salt with urea solution at room temperature, and react for 0.5-12 hours at a temperature of 80-120°C;

b) Filtration and washing process: filtering, washing and drying the synthesized solid product to obtain the nanostructure of dried cobalt hydroxide;

c) Calcination process: heat the product obtained in the filtration and washing process at a temperature of 200-400° C. for 1-2 hours, and cool to room temperature.

In the synthesis process, the preferred concentration of the divalent cobalt salt is 0.04-0.1 mol/L; the urea solution is 0.04-0.1 mol/L.

The divalent cobalt salts are cobalt chloride, cobalt nitrate and cobalt sulfate.

In the synthesis process of the present invention, in the initial stage of the reaction, the supersaturation of the aqueous solution is very high, the decomposition of urea and the nucleation and growth of CoOOH grains occur almost simultaneously, and the high supersaturation is conducive to the formation of CoOOH with a small particle size to have a polyhedral growth Morphology, these grains become the "nuclei" of the multipod-like CoOOH. With the continuous generation of small-sized CoOOH crystals, the supersaturation of the hydrothermal solution decreased. When it drops to a certain level, the polar growth of grains dominates, and finally multipod-like CoOOH crystals are formed on the "core", that is, the rod-cluster structure we get. When the concentration of urea decreases, the saturation of the solution is not very high, which is not conducive to the growth of polyhedrons of the "nuclei", which can only grow continuously in one direction, and finally obtain a linear structure.

The calcination process of the present invention is to convert the hydroxide precursor in the previous stage into a porous cobalt tetraoxide nanostructure, and the morphology of the product will not change.

The main technical indicators of the cobalt tetroxide one-dimensional porous nanomaterial with uniform particle size, small scale, good activity and high bulk density prepared by the present invention are shown in Table 1:

Table 1:

C _Co ²⁺ /C _urea (molar ratio) purity particle size Yield(%) Surface topography 1:1 >99% 40-60nm 94 porous nanowire 1:5 >99% 40-60nm 96 porous nanorod clusters 1:10 >99% 40-60nm 98 porous nanorods

Compared with the prior art, the present invention has uniform nano-powder particles, good dispersibility, and better cleanliness; only cobalt source is used as the precursor, and no crystal seed needs to be added; the yield is high, the cost is low, and the production process is short. The prepared tricobalt tetroxide has a very high specific surface area, which can greatly improve the performance of the battery when applied to the lithium ion battery.

Description of drawings

Fig. 1 is the X-ray diffraction (XRD) figure of the cobalt trioxide nanopowder that embodiment 2 makes.

Fig. 2 is the scanning electron microscope (SEM) picture (20,000 times) of the cobalt trioxide nanopowder that embodiment 2 makes.

Fig. 3 is the scanning electron microscope (SEM) photograph (100,000 times) of the cobalt trioxide nanopowder that embodiment 2 makes.

Fig. 4 is the transmission electron microscope (TEM) photograph (340nm) of the cobalt trioxide nanopowder that embodiment 2 makes.

Fig. 5 is the transmission electron microscope (TEM) picture (170nm) of the cobalt trioxide nanopowder that embodiment 2 makes.

Detailed ways

The technical solution of the invention will be further described below in conjunction with specific embodiments.

Example 1:

Under vigorous stirring, 1 mmol of cobalt chloride (CoC1 ₂ ) was weighed, added to 25 mL of distilled water, and 1 mmol of urea was added under continuous magnetic stirring to form a mixed solution. Then the mixed solution was heated at 80°C, and the reaction time was controlled for 1 hour. Then filter, wash, and dry in a 70°C drying oven for 30 minutes. Then calcined at 200° C. for 1 hour to obtain multifunctional cobalt tetraoxide nanowires with a purity of 100%, a particle size of 40 nm, and a yield of 87.2% by weight.

Example 2:

Weigh 1 mmol of cobalt chloride under vigorous stirring, add it into 25 mL of distilled water, and continue adding 1 mmol of urea under magnetic stirring to form a mixed solution. Then the mixed solution was heated at 100°C, and the reaction time was controlled for 1 hour. After filtering, washing, and drying in a drying oven at 70° C. for 5 hours. Then calcined at 300° C. for 1.5 hours to obtain multifunctional cobalt tetroxide nanorod clusters with a purity of 100%, a particle size of 50 nm, and a yield of 87.1% by weight.

Example 3:

Weigh 1 mmol of cobalt chloride under vigorous stirring, add it into 25 mL of distilled water, and continue adding 1 mmol of urea under magnetic stirring to form a mixed solution. Then the mixed solution was heated at 120°C, and the reaction time was controlled for 1 hour. Then filter, wash, and dry in a 70°C drying oven for 12 hours. Then calcined at 400° C. for 2 hours to obtain dispersed multifunctional cobalt tetroxide nanorods with a purity of 100%, a particle diameter of 50 nm, and a yield of 86.9% by weight.

Example 4:

Weigh 1 mmol of cobalt chloride under vigorous stirring, add it into 25 mL of distilled water, and continue adding 5 mmol of urea under magnetic stirring to form a mixed solution. Then the mixed solution was heated at 120°C, and the reaction time was controlled for 1 hour. Then filter, wash, and dry in a 70°C drying oven for 12 hours. Then calcined at 300° C. for 1 hour to obtain dispersed multifunctional cobalt tetraoxide nanorods with a purity of 100%, a particle diameter of 50 nm, and a yield of 87.3% by weight.

Example 5:

Weigh 1 mmol of cobalt chloride under vigorous stirring, add it into 25 mL of distilled water, and continue adding 10 mmol of urea under magnetic stirring to form a mixed solution. Then the mixed solution was heated at 120°C, and the reaction time was controlled for 1 hour. Then filter, wash, and dry in a 70°C drying oven for 12 hours. Then calcined at 300° C. for 1 hour to obtain dispersed multifunctional cobalt trioxide nanorods with a purity of 100%, a particle size of 55 nm, and a yield of 87% by weight.

Example 6

Under vigorous stirring, 1 mmol of cobalt nitrate (Co(NO ₃ ) ₂ ) was weighed, added to 25 mL of distilled water, and 5 mmol of urea was added under continuous magnetic stirring to form a mixed solution. Then the mixed solution was heated at 120°C, and the reaction time was controlled for 1 hour. Then filter, wash, and dry in a 70°C drying oven for 12 hours. Then calcined at 300°C for 1 hour to obtain dispersed multifunctional cobalt tetroxide nanorods with a purity of 100%, a particle size of 60 nm, and a yield of 87.1% by weight.

Embodiment 7:

Under vigorous stirring, 1 mmol of cobalt sulfate (CoSO ₄ ) was weighed, added to 25 mL of distilled water, and 5 mmol of urea was added under continuous magnetic stirring to form a mixed solution. Then the mixed solution was heated at 120°C, and the reaction time was controlled for 1 hour. Then filter, wash, and dry in a 70°C drying oven for 12 hours. Then calcined at 300° C. for 1 hour to obtain dispersed multifunctional cobalt tetraoxide nanorods with a purity of 100%, a particle size of 55 nm, and a yield of 87.2% by weight.

Embodiment 8:

Electrochemical performance test:

(1) Mix the nano-cobalt trioxide powder prepared in Examples 1-7 with acetylene black and polytetrafluoroethylene in a mass ratio of 50:40:10, and press the electrode active material on the copper sheet under a pressure of 20 MPa , the diameter of the working electrode produced is 1cm, the metal lithium sheet is used as the auxiliary electrode, the diameter is 1cm, the calomel electrode is used as the reference electrode, the electrolyte is 1mol/L lithium hexafluorophosphate dissolved in the mixed solution of ethylene carbonate and dimethyl carbonate, carbonic acid The molar ratio of vinyl ester to dimethyl carbonate is 1:1;

(2) Battery assembly: the entire battery assembly is completed in a glove box filled with argon;

(3) Electrochemical performance test: The whole battery is completed with the LAND battery test system.

The test results show that the electrochemical performance of Examples 1-7 is very good, and the specific capacity can still be maintained above 1300mAh/g after 20 cycles.

Claims (4)

1. The preparation method of porous one-dimensional nanometer cobalt tetroxide, characterized in that: comprising the following steps: a) Synthesis process: mix divalent cobalt salt with urea solution at room temperature, and react for 0.5-12 hours at a temperature of 80-120°C; b) Filtration and washing process: filtering, washing and drying the synthesized solid product to obtain the nanostructure of dried cobalt hydroxide; c) Calcination process: heat the product obtained in the filtration and washing process at a temperature of 200-400° C. for 1-2 hours, and cool to room temperature. 2. The method for preparing porous one-dimensional nano-cobalt tetroxide according to claim 1, characterized in that: in the synthesis process, the concentration of the divalent cobalt salt is 0.04-0.1 mol/L. 3. The preparation method of porous one-dimensional nano-cobalt trioxide according to claim 1, characterized in that: in the synthesis process, the urea solution is 0.04-0.1mol/L. 4. The method for preparing porous one-dimensional nano-cobalt tetroxide according to claim 1 or 2, characterized in that in the synthesis process, the divalent cobalt salts are cobalt chloride, cobalt nitrate and cobalt sulfate.

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